As exemplary automatic analyzer that inhibits reagent deficiency from occurring during analysis to minimize analysis interruption, reducing the burden on an operator due to operations, such as reagent registration and reagent replacement, PTL 1 describes an automatic analyzer including: pairs of reagent containers provided in a line in a replenishing reagent storage cabinet including a replenishing second reagent storage unit above a reagent disk, the replenishing reagent storage cabinet being capable of being equipped with a plurality of reagent containers; a rail arranged on the replenishing reagent storage cabinet; and a reagent retaining unit and a reagent cap opening unit provided on the rail, the reagent retaining unit and the reagent cap opening unit being movable together with the rail in a triaxial direction.